1. Field of the Invention
The present invention relates to the field of adjustable pressure relief valves for use in hydraulic circuits, particularly for controlling pressure transients—acceleration and deceleration—of hydraulic motors subject to inertia forces (progressive anti-shock pressure relief valves).
2. Description of the Related Art
Adjustable pressure relief valves are widely used in the art.
Such pressure relief valves have the purpose of damping regulating pressure increases by compressing a main spring via a spring pressing member actuated by the pressure of hydraulic fluid carried from the feed line into a chamber above it. An adjusting spring is also mounted in such chamber, for downwardly pressing the movable member within the pressure relief valve; the force with which such adjusting spring operates on the movable member may be adjusted by operating an adjustment means situated outside the valve.
Thus, the valve may be easily adjusted.
The main drawback of the prior art is that, due to considerable leakages, these valves mounted to hydraulic motors with transient control and anti-shock purposes cannot prevent the hydraulic motor from rotating when it is subject to a driving load and is not powered; therefore, additional motor braking systems shall be provided to prevent load displacement while the machine in which the motor is mounted is still.
A further drawback of prior art pressure relief valves is their complex construction architecture and the large number of their components.